This invention relates to methods for the recovery of metal values from lead smelter matte and, in particular, to the recovery of copper, nickel and cobalt therefrom.
At the present time, mattes produced at lead smelters are either being shipped overseas or to U.S. copper smelters for recovery of copper only. No attempt is presently being made, on a commercial scale, to recover the cobalt and nickel in the United States. Several methods have been developed to recover cobalt, nickel, and copper from mattes, other than lead mattes.
Ammoniacal and acid pressure leaching are most commonly used. These methods require pressures greater than atmospheric, requiring expensive high pressure autoclaves. Reaction times as long as ten hours are required to obtain complete reaction. In ammoniacal solutions, the cobalt content must be kept low because of the formation of insoluble cobaltic hexamine sulfate. This makes it necessary to have larger process streams for cobalt dilution.
Copper-nickel converter mattes are being treated by a strong hydrochloric acid leach which selectively dissolves the nickel as the chloride, leaving the copper and other metals in residue. This procedure has the disadvantages that H.sub.2 S is formed and chloride solutions are highly corrosive.
It is an object of the present invention to provide a process for the recovery of metal values from lead smelter matte. It is a further object to provide such a process for the recovery of copper, nickel and cobalt values therefrom. It is yet a further object to provide such a process which includes an acid leaching step which can be carried out at atmospheric pressure in relatively inexpensive equipment.